If ap_slack fails to allocate above the low slack line it's a good

indication that further problems will occur; it's a better indication
than many external libraries give us when we actually run out of
descriptors.  So report it to the user once per restart.

PR:		1181
Reviewed by:	Jim Jagielski, Ken Coar


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@79553 13f79535-47bb-0310-9956-ffa450edef68